The present exemplary embodiment relates to a flexible media transport system. In particular, it relates to a printing or copying system with a lookaside path which enables movement of paper sheets into or out of a main paper path and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
In a typical copying/printing apparatus, a photoconductive insulating member is charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member, which corresponds to the image areas contained within the document. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with developing powder referred to in the art as toner. This image may subsequently be transferred to a support surface, such as copy paper, to which it may be permanently affixed by heating and/or by the application of pressure, i.e., fusing.
In a conventional printing apparatus, sheet material or paper is handled by a series of rollers and counter rollers. The counter roller generates forces normal to the tangential surface of a roller for handling the sheet. Counter rollers, however, sometimes lead to jams, paper tears, wrinkling, or other surface damage to the sheet. The normal operation of the printer may be interrupted for some time while the damaged sheets are removed.
Traditional rollers form what is know in the field as a non-holonomic sheet transport system because only a limited number of directions of movement are possible for the sheet at a given time. Where sheets are to be merged, an interposer or sheet inserter is used. Examples of such sheet inserters are disclosed, for example, in U.S. Pat. No. 6,559,961 to Isernia, et al. and U.S. Pat. No. 5,995,721 to Rourke, et al. Isernia, et al. discloses a system for printing jam-prone sheets. These are printed as separated pages prior to printing any of the other electronic pages. The system temporarily holds them in an interposer, then prints the other pages of the document onto normal sheets, and provides collated merging in the interposer to provide collated output of the entire electronic document. Rourke, et al. discloses a queuing system for examining document attributes and delivering one or more portions of the document to one or more document processing subsystems and then merging the document portions.
Reconfigurable printing systems increasingly consist of multiple parallel, alternative modules that are connected through flexible paths or loops. Such systems offer a multitude of alternative operations (or capabilities) to produce the same or different outputs. For example, a modular printing system may consist of several identical, parallel printers connected through flexible paper paths that feed to and collect from these printers.
U.S. Pat. Nos. 6,607,320 to Bobrow, et al., and U.S. Pat. No. 6,554,276 to Jackson, et al., which are incorporated herein in their entireties by reference, disclose an apparatus for processing a substrate on two sides. The apparatus of Bobrow includes an input pathway for receiving the substrate from a substrate processing station, a station for processing the face-up side of the substrate, a reversion pathway for reverting the substrate and returning the reverted substrate to the input pathway. A merge point merges the reverted substrate into the input pathway for processing the face-up side of the substrate in the print station. The substrate is manipulated in the reversion pathway by a plurality of air jets. In such systems, all the sheets start and finish on the input pathway and those that have passed along the reversion pathway are changed in their orientation.